As far as I know, there are many idioms and sayings originated from the Bible, myths, Greeks, Latins or exotic anecdotes. So if stories behind such idioms and sayings could be provided for, I think it would be very helpful for us idiom-beavers to memorise them. What do you think about this, our honourable webmaster?
To illustrate, "to cross the Rubicon" is one of them which have a story to tell.